The present invention relates to an electric motor and to an electric type compressor, which is formed by integrating the electric motor with a compression mechanism.
Japanese Unexamined Patent Publication No. 2003-56463 discloses electric type compressors, which are integrally provided with an electric motor, and are used in a vehicle air conditioning apparatus. In the electric type compressor, a circular stator core for the electric motor is tightly fitted inside of a cylindrical housing by shrink fit and press fit. Since the fixation of the stator core by the tight fit is relatively simple and easy, the associated cost of the electric type compressor is lowered.
However, if an aluminum housing is used to reduce the weight of the electric type compressor, since the thermal expansion coefficient of the housing is different from that of the stator core made of iron, a degree of tightness between the stator core and the housing changes in accordance with a temperature change of the electric type compressor. Note that thermal expansion coefficient of aluminum is larger than that of iron. The interference between the housing and the stator core is predetermined in such a manner that the housing and the stator core are not loose with each other even when the temperature of the electric type compressor becomes relatively high. Therefore, on the contrary, when the temperature of the electric type compressor becomes relatively low, the degree of tightness is excessively increased and the housing and/or the stator core generate a crack.